1. Field Of The Invention
The invention concerns a connection method for two optical fibres having the same diameter with a view to forming a permanent optical link between these two fibres.
2. Description Of The Prior Art
The foreseeable development of telecommunications by guided optical waves makes it desirable to produce devices making it possible to connect together two optical fibres with coupling losses which are as low as possible, for example less than 1 db. If the fibres have, for example, a core with a diameter of 100 microns having a lower optical index, with a difference in index between core and casing comprised between 5.10.sup.-.sup.3 and 10.sup.-.sup.1, these devices must then allow the positioning of the fibres in the following conditions: distance between the ends facing the fibres less than 20 microns; relative excentricity less than 4 microns; relative inclination less than 1.degree. . In the case where an adaptation of the index is effected, these tolerances become greater: 50 microns for the distance and 10 microns for the excentricity, the inclination being unchanged. Taking into account the slight diameter of the fibres, these tolerances are difficult to keep to.
The solutions proposed up to this day are very few and are generally related to laboratory installations.
The article by D. SCHICKETANZ, "Connectors for multimode fibres" (Siemens Forschung; Entwickl Ber. Bd 2 (1973) No. 4) proposes a connection between fibres through a glass capillary tube, which is swaged over given length with an inside diameter slightly greater than the outside diameter of the fibre. The capillary tube, having an index close to that of the casing of the fibre, contains either a liquid or a solid element, having an index close to that of the core of the fibre. The main characteristic is that the connector is itself an optical wave guide.
According to the article by C.G. Someda, "Simple, Low-loss joints between single-mode optical fibres" (Bell System Technical Journal Vol. 52 No. 4, April, 1973), the alignment between the optical fibres is effected by means of a groove obtained by swaging a methyl polymethacrylate sheet by means of a fibre having the same diameter.
According to French patent No. EN 73 11 188 applied for on 28th March, 1973, by WESTERN ELECTRIC COMPANY, INCORPORATED, for a "Device for connecting optical fibres", connecting is effected by deformation of a silicone elastomer web, which is drilled with a hole in which the fibres are engaged. Blocking is effected by pressure on two plates placed on either side of the web. The supposed result is the simultaneous alining and immobilizing of the fibres.
The article by Frank L. Thiel, Roy E. Love, Rex L. Smith, "In line connectors for multimode optical waveguide bundles" (Applied optics, Vol. 13, No. 2, February, 1974, page 240) proposes a connector structure between two cables each comprising a compact hexagonal stacking of the fibres in casing having a corresponding hexagonal inside cross-section. The aligning of the fibres results from the aligning of the casings of the two cables.
The aim of the present invention is to make it possible to ensure a permanent link between two optical fibres with a particularly great accuracy with respect to the aligning of these two fibres.